The present invention relates to a honeycomb structure that supports activated carbon and which has the ability to adsorb or decompose gases. The present invention also relates to a process for fabricating such a honeycomb structure.
When large volumes of gas are to be treated with activated carbon in an attempt at adsorbing or decomposing a certain component of the gas, it is desirable that the activated carbon used as the treatment medium should experience the lowest possible pressure loss. To satisfy this need, JP-A-60-90808 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") has proposed that a material for activated carbon be extruded in a honeycomb shape, carbonized and further activated for use as activated carbon in decomposing the ozone in an ozone-containing gas. This honeycomb structure has an activated carbon loading of 300 g per liter of unit volume and assures high performance as evidenced by a benzene or methanol adsorption of 50 mg/L and an ozone decomposition efficiency of 85% after the passage of 80 h. However, it is difficult to fabricate large and robust honeycomb structures by extrusion molding and the applicable structure that is proposed in JP-A-60-90808 has been limited to small sizes. In addition, this practically all carbon honeycomb structure has had the following disadvantages in spite of large adsorption capacity per unit weight; because of the tendency of activated carbon to consolidate, not all of the activated carbon provides an effective surface for adsorption; a cumbersome treatment is necessary such as activation that follows shaping; the honeycomb structure is prone to cracking and requires very careful handling; the structure is too expensive to be used in various fields.
A method is also known in which paper is made from a mixture or organic fibers (e.g. pulp) and activated carbon and a honeycomb structure is fabricated from the resulting activated carbon containing paper. However, this method is unable to achieve a high loading of activated carbon (the maximum will be about 70 g per liter of paper volume) and the honeycomb structure fabricated has not been satisfactory in terms of adsorption capacity or service life.